System for controlling light in dependence of time-of-flight signal

ABSTRACT

A lighting system comprising a lamp arranged to transform electricity into a light beam having different properties; a light control system arranged to adjust said light beam properties; an ultrasonic transmitter arranged to transmit ultrasonic signals; an ultrasonic receiver arranged to receive reflected ultrasonic signals; and a processing system arranged to derive a time-of-flight signal representing the time differences between said transmitted and received ultrasonic signals and to send control signals to said light control system in dependence of said time-of-flight signal. The processing system performs a reference calibration step: the time-of-flight is repeatedly measured a multitude of times, and calculates the average of said measured time-of-flight values and stores the average in memory system as a reference time-of-flight value if said deviation of the majority of the measured time-of-flight values of said multitude of measurements is lower than a predetermined threshold.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to PCT Application entitled “Robust 1DGesture Light Control Algorithm,” having serial numberPCT/CN2007/003050, filed on Oct. 26, 2007, which is incorporated byreference in its entirety.

FIELD OF THE INVENTION

The invention relates to a lighting system comprising a lamp arranged totransform electricity into a light beam having properties such asintensity, colour, colour temperature, direction and beam cone angle,and a light control means arranged to adjust said light beam properties.

BACKGROUND OF THE INVENTION

Adjustment of a lamp's properties is well known to be achieved via aremote control (RC). A disadvantage of a remote control is the necessityof the presence of the remote control on the right location at a randommoment. Also a lot of different remote controls are already present inthe living room for TV, audio, VCR, CD/DVD player/recorder, etc.Further, the different buttons on a remote control can be confusing tothe user. Finally, the costs of a remote control and the accompanyingreceiver are relatively high.

Also control of electrical devices by the use of video cameras andmovement detection software is known, wherein the user can control theelectrical device by making gestures in front of the camera. Suchsystems require heavy duty processing power, have a relatively longresponse time, and are relatively expensive.

WO 2006/056814 describes a lighting system comprising a lamp and acontrol means comprising an infrared transmitter, an infrared receiverand a lens arrangement. The control means measure the intensity of thereflected infrared light, and changes the lamp brightness in reactionthereto. In this manner the lamp can be switched on and off, and can bedimmed by hand movements in the infrared beam. Such an arrangement ishowever relatively expensive and inaccurate, as the intensity of thereflected infrared signal heavily depends on the kind of object that ismoved in the beam.

It is a goal of the invention to provide an improved, cheap, reliableand easy-to-use control system for lighting. A further goal of theinvention is to provide a lighting system that is safe and comfortablefor its users and their environment.

SUMMARY OF THE INVENTION

According to the invention the lighting system further comprises anultrasonic transmitter arranged to transmit ultrasonic signals, anultrasonic receiver arranged to receive reflected ultrasonic signals,and a processing means arranged to derive a time-of-flight signalrepresenting the time differences between said transmitted and receivedultrasonic signals and to send control signals, for instance binarycode, to said light control means in dependence of said time-of-flightsignal. Thereby a user of the system can adjust the lamp properties bymoving an object, such as his hand, in the ultrasonic beam.

The ultrasonic transmitter may for instance emit sound at a frequency of40 kHz. Although alternatives to the use of ultrasonictransmitters/receivers, such as for instance infrared or radartransmitters/receivers would be capable of measuring the time-of-flightof the respective signals, ultrasound is in particular suitable for thepresent application, since the time-of-flight (where the typicaldistance is between 0.2 and 2 meter) can be measured in millisecondsrather than in nanoseconds, which allows for easy and accuratemeasurement with low cost processing equipment. The system of theinvention can be produced at very low cost, since piezoelectric acoustictransducers are very cheap.

GB-A-2 291 289 describes a lighting system comprising a control meansfor switching a lamp on and off and for dimming the lamp, whereinpiezoelectric ultrasonic transmitters and receivers are used to detectthe presence of an object in the vicinity of the lamp, and said controlmeans is arranged to react to the presence of said object. This systemdoes however not use time-of-flight measurements of the ultrasonicsignal, and thereby is not able to react to movement of the object.

The system of the invention is easy to control, with a simple userinterface which does not require additional equipment such as a remotecontrol. Other qualities of the system of the invention are itsrobustness, its independency from environmental conditions, itsone-dimensional recognition of control movements, and its low processingpower requirements. The further advantage of an ultrasound sensor isthat it is less influenced by changing ambient light, temperature andhumidity conditions.

The processing means is preferably arranged to analyse the dynamicbehaviour of said time-of-flight signals and to send control signals tosaid light control means in dependence of said dynamic behaviour.Thereby the user can make gestures in the ultrasonic beam that will berecognised by the processing means and translated into control signals.

Said processing means is preferably arranged to stop sending controlsignals if said time-of-flight signal changed from dynamic behaviour toa value that has been substantially constant for a first predeterminedperiod of time, said first predetermined period of time preferably beingin the range of 0.5-2 s. By switching off the sending of control signalsit is possible to prevent accidental adjustment of the lamp propertiesby a moving object. In order to turn the sending of control signals on,said processing means is further preferably arranged to determine andstore a highest reference value, which reference value is determined asthe value that has been present during most of a second predeterminedlonger period of time of for instance several minutes, and saidprocessing means is then further arranged to start sending controlsignals if said time-of-flight signal changed from said highestreference value to a lower value that has been substantially constantfor at least a shorter third predetermined period of time, said thirdpredetermined period of time preferably being in the range of 0.5-2 s.

In the preferred embodiment said lamp is a spotlight type lamp arrangedto emit a light beam having a beam cone angle θ smaller than 45°,preferably smaller than 30°. Said beam cone angle of the transmittedultrasonic signals is preferably smaller than 15°. To that end saidultrasonic transmitter may comprise a horn for reducing the beam coneangle of the transmitted ultrasonic signals.

In the preferred embodiment said ultrasonic transmitter and receiver arearranged to transmit and receive ultrasonic signals in a directionextending within the light beam of the lamp. The light source of saidlamp is preferably a plurality of LEDs, wherein said ultrasonictransmitter and receiver preferably extend substantially between saidplurality of LEDs.

Said ultrasonic transmitter and receiver, processing means, and/or lightcontrol means, preferably extend in the lamp housing, and saidultrasonic transmitter and receiver preferably are a combined ultrasonictransducer. Thereby a compact and easy to install lighting system isprovided, that is intuitively controlled by moving one's hand in thecentre of the light beam. The invention also relates to a single lampunit comprising the entire lighting system as described above.

According to a further aspect of the invention, in order to adjust thesound pressure of the ultrasonic transmitter to an acceptable,un-harmful and comfortable level for the users of the lighting systemand their environment, said processing means is further arranged toperform a sound pressure level calibration step wherein the amplitude ofthe received reflected ultrasonic signal of the receiver is measured andwherein the amplitude of the transmitted ultrasonic signal of thetransmitter is adjusted such that the amplitude of the receivedreflected signal approximates a predetermined threshold value. Theamplitude of the received reflected ultrasonic signal in a certainsituation depends on the transmitted amplitude, the distance-of-travel,the environmental absorption (e.g. absorption of ultrasound by air), andthe diffraction by the reflecting reference surface (e.g. a fixed table,floor, etc.). In a certain situation for the period that the lamp isswitched on it can be assumed that the absorption and diffraction areeither constant if no object moves into the ultrasonic beam, or that thereceived amplitude will increase because the reflecting object is closerto the ultrasonic receiver, and therefore after calibration thetransmitted amplitude can remain constant while it is more or lessensured that the received signal is always higher than the requiredthreshold. In case however that after calibration the lighting systemdoes (sometimes) not react to control gestures of the user, the user canbe instructed to calibrate the system while holding the control object(f.i. his hand) at the farthest point he is expecting to put said objectfor controlling the system.

The transmitted and received sound pressure levels are measured in dB,but can be represented by a voltage, for instance the voltage put on theultrasonic transmitter or the voltage received from the ultrasonicreceiver. The maximum permissible exposure to 40 kHz ultrasound forinstance is set by various organisations around 100 dB. The inventionaims however at much lower levels than this, and will adjust thepressure level to a minimum, yet optimum level.

In order to further reduce the influence of the acoustic pressure on theusers, the system is arranged to transmit said ultrasonic signalsintermittently in short (preferably max. 100 ms) intervals.

Said processing means is preferably arranged to perform said soundpressure level calibration step in a short period, for instance withinthe first few seconds, after the lamp is switched on. Further saidprocessing means is preferably arranged to start deriving saidtime-of-flight signal and sending control signals after said soundpressure level calibration step. Furthermore preferably said processingmeans is arranged to repeatedly perform said sound pressure levelcalibration step while it is deriving said time-of-flight signals and issending said control signals to said light control means. Thereby adynamic calibration of the sound pressure level to the lowest level thatis necessary to operate the system is achieved.

In order to achieve the minimum necessary sound pressure level for thesystem to work properly, said processing means is preferably arranged tostart said sound pressure level calibration step with a firstcalibration cycle wherein the ultrasonic transmitter is caused to sendan ultrasonic pulse with a predetermined lowest amplitude and whereinthe amplitude of the received reflected signal is measured, and torepeat said calibration cycle with a transmitted amplitude that isincreased in each subsequent cycle with a predetermined value as oftenas necessary until the amplitude of the received reflected signal isequal to or higher than said predetermined threshold value. Saidprocessing means is preferably arranged to cause a warning signal to beemitted by said lighting system, for instance a flickering of said lamp,if the amplitude of the received reflected signal is lower than saidpredetermined threshold value after a predetermined maximum number ofcalibration cycles.

There are several issues related to the robustness and reliability of agesture light control system based on ultrasound. Reflections,diffraction, interference, noise may disturb the received signal. Otherissues like a moved reference surface, other moving objects, multipleobjects should be dealt with.

According to a further aspect of the invention, in order to provide arobust and reliable system, said processing means is further arranged toperform a reference calibration step, wherein the time-of-flight (TOF)is repeatedly measured a multitude of times, and wherein the processingmeans determines if the deviation of the majority of the measuredtime-of-flight values (TOFI) of said multitude of measurements is lowerthan a predetermined threshold (z), and wherein said processing means isarranged to calculate the average (TOFREF) of said measuredtime-of-flight values (TOFI) and store said average (TOFREF) in memorymeans as a reference time-of-flight value if said deviation is lowerthan said threshold (z). Said processing means is preferably arranged togenerate an error signal if said deviation is not lower than saidthreshold (z).

Preferably said processing means is arranged to store said referencetime-of-flight value (TOFREF) in said memory means only if saidreference time-of-flight value (TOFREF) is greater than a predeterminedminimum value. Said processing means is preferably arranged to generatean error signal if said reference time-of-flight value (TOFREF) is notgreater than said predetermined minimum value.

Preferably said processing means is arranged not to store a referencetime-of-flight value (TOFREF) in said memory means if during saidreference calibration step no signal is received by said ultrasonicreceiver during at least a predetermined number of time-of-flightmeasurements. Said processing means is preferably arranged to generatean error signal if during said reference calibration step no signal isreceived by said ultrasonic receiver during at least said predeterminednumber of time-of-flight measurements.

According to a further aspect of the invention, in order to provide arobust and reliable system, said processing means is arranged to performa wait-for-control-enablement cycle wherein said time-of-flight (TOF) isrepeatedly measured at predetermined intervals and to compare saidmeasured time-of-flight value (TOF) with a reference time-of-flightvalue (TOFREF) which is stored in memory during said wait-for-controlcycle, and to repeat said measurement if said measured time-of-flightvalue (TOF) is equal to or larger than said reference time-of-flightvalue (TOFREF), said processing means is further arranged to determineif the measured time-of-flight value (TOF) is smaller than saidreference time-of-flight value (TOFREF) and if the deviation between themeasured time-of-flight value (TOFH) and the previous measuredtime-of-flight value (TOFH−1) is lower than a predetermined threshold(tx), and said processing means is arranged to send control signals tosaid light control means in dependence of time-of-flight signals derivedafter it is determined that the measured time-of-flight value (TOF) issmaller than said reference time-of-flight value (TOFREF) and that saiddeviation is lower than said threshold (tx) for a predetermined numberof repeated measurements.

Said predetermined interval is preferably substantially larger if it isdetermined that said measured time-of-flight value (TOF) is equal to orlarger than said reference time-of-flight value (TOFREF), than if it isdetermined that said measured time-of-flight value (TOF) is smaller thansaid reference time-of-flight value (TOFREF).

Preferably said processing means is arranged to calculate the average ofsaid measured time-of-flight values (TOF) and to store said average(TOFH) in memory means, and the processing means is arranged to sendcontrol signals to said light control means in dependence on thepositive or negative difference between the measured time-of-flight(TOF) and said average time-of-flight (TOFH) after it is determined thatsaid deviation is lower than said threshold (tx) for a predeterminednumber of repeated measurements.

Preferably said processing means is further arranged to clip thedifference of the measured time-of-flight value (TOF) to a maximumallowed positive or negative difference between the measuredtime-of-flight (TOF) and said average time-of-flight (TOFH) for thepurpose of determining the control signals to be sent to the lightcontrol means.

Preferably said processing means is further arranged to calculate saidmaximum allowed positive and negative difference such that the negativedifference is smaller than said average time-of-flight (TOFH), and thatthe positive difference is smaller than the difference between saidreference time-of-flight (TOFREF) and said average time-of-flight(TOFH).

Preferably said processing means is further arranged to adapt thedetermination of the control signals to be sent to the light controlmeans such, that the full range of control signal can be achieved withinthe calculated range of the maximum allowed positive and negativedifference.

According to a further aspect of the invention, in order to be able toadjust different light beam properties, said processing means and saidlight control means are further arranged to change from adjustment ofone of said light beam properties to adjustment of another one of saidlight beam properties, if a predetermined behaviour in saidtime-of-flight signal is determined.

In a preferred embodiment said behaviour is a series of subsequentlymeasured time-of-flight values that is substantially constant during apredetermined period.

In a further preferred embodiment said behaviour is a predeterminednumber of alternations of high and low measured time-of-flight values.

In a still further preferred embodiment said behaviour is apredetermined number of alternations of the presence and absence ofmeasured time-of-flight values.

In a remote controlled lighting system it is desirable to providefeedback about the status and working of the system to the user in anefficient and low-cost manner.

The invention therefore further relates to a lighting system comprisinga lamp arranged to transform electricity into a light beam havingproperties such as intensity, colour, colour temperature, direction andbeam cone angle; a light control means arranged to adjust said lightbeam properties; a processing means arranged to send control signals tosaid light control means; a user control interface arranged to transformuser control input into electronic input signals and to send thoseelectronic input signals to said processing means; wherein saidprocessing means is arranged to send a user feedback signal to saidlight control means such that said lamp properties either alternate intime or are different in adjacent locations, such that a user canrecognize said alternating or adjacent different light properties as afeed back signal.

Preferably said processing means is arranged to send said user feedbacksignal to said light control means for a short period of time, forinstance 0.2-5 seconds, and to send subsequently a signal to said lightcontrol means such that said lamp properties return back to the previousstate or are set to a predefined steady state such as the switched offstate.

In a preferred embodiment said feedback signal is such that the lampintensity is visibly changed at least twice within said short period oftime.

In a further preferred embodiment said feedback signal is such that thecolour temperature is visibly changed at least twice within said shortperiod of time.

In a still further preferred embodiments said lamp comprises an array ofLEDs, wherein said light control means is arranged to individually powersaid LEDs in said LED array, and wherein said feedback signal is suchthat a visible sign such as a letter or an icon is formed in said arrayduring said short period of time. Preferably said lamp comprises a lensto project said LED array on a reference surface. Said lens ispreferably adjustably mounted in said lamp such that it is adjustable independence of the measured distance between the lamp and the referencesurface.

In the preferred embodiment said user control interface comprises anultrasonic transmitter arranged to transmit ultrasonic signals; anultrasonic receiver arranged to receive reflected ultrasonic signals;wherein said processing means is arranged to derive a time-of-flightsignal representing the time differences between said transmitted andreceived ultrasonic signals and to send control signals to said lightcontrol means in dependence of said time-of-flight signal. Saidultrasonic transmitter and/or receiver is preferably built-in in thecentre of the lens.

It is desirable that the ultrasound controlled lighting system is easyto produce in mass quantities, with low cost components, and has smalldimensions so that it can be built-in in even in a small lamp.

The invention therefore further relates to a lighting system comprisinga lamp comprising an array of LEDs arranged to transform electricityinto a light beam having properties such as intensity, colour, colourtemperature; a light control means comprising a LED driver and a pulsewidth modulator arranged to adjust said light beam properties; aDA-converter, an ultrasound driver and an ultrasonic transmitterarranged to convert a digital transmit signal into the transmission ofan ultrasonic pulse; an ultrasonic receiver and an amplifier arranged toreceive reflected ultrasonic signals and transform said ultrasonicsignal in a voltage, and a comparator arranged to generate a digitalreceive signal if said voltage is greater than a predeterminedthreshold; a processing means arranged to derive a time-of-flight signalrepresenting the time differences between said digital transmit andreceive signals and to send control signals to said light control meansin dependence of said time-of-flight signal, wherein said processingmeans, said pulse width modulator, said DA-converter and said comparatorare integrated in a single microcontroller chip.

Said microcontroller chip is preferably chosen from the single-chip8-bit 8051/80C51 microcontroller family, preferably comprising smallsized RAM and ROM, preferably smaller than 4 kB ROM and smaller than 512B RAM.

Preferably said ultrasonic transmitter and said ultrasonic receiver areintegrated in a piezoelectric ultrasound transducer.

Preferably said transmitting ultrasound driver and said receivingultrasound amplifier are integrated in a pre-processing circuit. Saidpre-processing circuit preferably further comprises a second orderfilter for filtering out low frequent signals from said received signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further explained by means of a preferredembodiment as shown in the accompanying drawings, wherein:

FIG. 1 is a graph showing the principle of time-of-flight measurementwith an ultrasonic transceiver;

FIG. 2 is a schematic perspective view of the lamp and its controlmechanism;

FIG. 3 is a combined drawing showing stills of hand movements in thesystem of FIG. 2 and a graph showing the time-of-flight signal againsttime, and various stages of lamp property control caused by said handmovements;

FIG. 4 is a schematic perspective view of the lamp of FIG. 2;

FIG. 5 is a schematic top view of an average hand;

FIG. 6 is a three-dimensional graph showing beam radius against beamangle and vertical distance;

FIG. 7 shows schematically the movement of a hand in and out of the beamand the related graph of the time-of-flight against time;

FIG. 8 is a schematic cross-sectional view of an ultrasonic transducerand a horn;

FIG. 9 is a flow chart showing the calibration process of the lampsystem;

FIG. 10 is a combined drawing showing graphs of the voltage of thetransmitted ultrasound pulse signals, the voltage of the receivedreflected signals and the status of the sound pressure level calibrationin time;

FIGS. 11A-11C shows schematically the movement of a hand in and out ofthe beam;

FIG. 12 shows schematically the movement of a vase in the beam and therelated graph of the time-of-flight against time and the various phasesof control;

FIGS. 13-18 and 20-21 show flow charts of various control algorithms;

FIG. 19 schematically shows the determination of the control range;

FIG. 22 schematically shows the control mechanism of different lightproperties in time;

FIGS. 23-28 schematically show the control mechanism of different lightproperties in various stages;

FIGS. 29 and 30 show schematically the movement of a hand in the beamand the related graph of the time-of-flight against time;

FIG. 31 schematically shows a LED array lamp showing a message;

FIG. 32 schematically shows a LED array lamp projecting a message on areference surface;

FIGS. 33 and 34 schematically show an electronic hardware implementationof the invention; and

FIG. 35 is a perspective view of a lamp according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The lamp 1 as shown in FIG. 2 comprises a plurality of LEDs and anultrasonic transceiver built-in in the centre of said plurality of LEDs.Also a processing means for translating the signals of the transceiverinto control signals, and control means to adjust the light propertiesare built-in.

If the ultrasonic transceiver is switched on it will send an acousticsignal. If an object is present the acoustic signal will be reflected atthe object and will be received by the ultrasonic transceiver inside thelamp. The time difference, called the time-of-flight, between sendingand receiving the acoustic signal will be measured. If the distancebetween the object and the lamp 1 is changed another time-of-flightvalue will be measured. The detected movement of the object is aone-dimensional movement (the object must stay in the ultrasound beamcone). The change in time-of-flight will be translated into a change ina digital control signal. This control signal will control theproperties of the light beam, like colour, intensity or colourtemperature, etc.

The object may be the hand 2 of a user. Thus a one-dimensional movementof the hand 2, like up/down or left/right direction (depending on lampposition, horizontal or vertical) can control the light beam properties.

In commercially available pulse echo distance measurement units of thetransmitter-reflector-receiver type (TRR), the most common task is tomeasure the distance to the closest reflecting object. The measured timeis the representative of travelling twice the distance. The returnedsignal follows essentially the same path back to a receiver locatedclose to the transmitter. Transmitting and receiving transducers arelocated in the same device. The receiver amplifier sends these reflectedsignals (echoes) to the micro-controller which times them to determinehow far away the object is, by using the speed of sound in air.

The time-of-flight of acoustic signals is commonly used as a distancemeasurement method. A time-of-flight measurement, as illustrated in FIG.1 is formed by subtracting the time-of-transmission (T in FIG. 1) of asignal from the measured time-of-receipt (R in FIG. 1). This timedistance information will be transferred into a binary code in themicroprocessor to control the lamp properties.

In FIG. 2 a hand 2 is the obstacle/object and a table 3, floor orceiling is the reference. The ultrasonic transducer sends an ultrasonicwave in the form of a beam cone 4. If the distance y from the transducerto the reference is 1.5 m, the total travel distance for the ultra-soundbeam 4 is 2*y=3 m. The time-of-flight then is 8.7 ms (at an ambienttemperature of 25° C.). If the distance x from the transducer to thehand is 0.5 m, the time-of-flight is 2.9 ms. If the required accuracy ofcontrol steps of the hand movement is 2 cm (time-of-flight steps of 0.12ms), and the range of control is for instance 64 cm, there are 32control steps, which allows for 5-bit control.

The control signal as shown in FIG. 3 is made by the movement of thehand 2 in a one-dimensional vertical direction in the ultrasonic beam 4.At T1=1 s the hand 2 is outside the beam, the reference value ismeasured, and lamp control is disabled (stage A). At T2=2 s the hand 2moves into the beam 4 and is held there for more than 1 second until atT3=3 s lamp control is enabled by the microcontroller (stage B). Thenthe hand 2 moves up between T3=3 s and T5=5 s, whereby for instance theintensity of the lamp 1 is increased by the microprocessor (stage C). AtT6=6 s the hand is withdrawn from the beam 4 so that the reference valueis measured, and lamp control is disabled thereby (stage D). Anaccidental movement of the hand 2 in the ultrasonic beam 4 as shown atT7=7 s does therefore not result in an accidental adjustment of the lampproperties (stage E). Hence, the lamp control is activated by holding anobject in the ultrasonic beam 4 for more than 1 second.

The ultrasonic beam cone angle is important to provide reliable handcontrol. In FIG. 4 the beam radius at the reference position is r. Thebeam radius rh at the hand position must be high enough to have optimumcontrol by hand. During control of a lamp property the average beamradius should be equal to approximately half the length of the averagehand shape as shown in FIG. 5. If the total control range is around X/2(for a lamp/table application), the ultrasound beam angle at the minimumbeam radius during control of the lamp property will be around Lh/2. Forexample: if Lh=150 mm and X=1.5 m, the ultrasound beam angle θ should be11°. The relationship between the vertical distance X and the beam angleas function of the beam radius is shown in FIG. 6. Lamp control will bepossible if the hand 2 is in the narrow ultrasound cone 4 as shown inFIG. 7. Reduction of a wide ultrasound beam 4 and an increase of soundpressure level (SPL) of an ultrasonic transducer 5 may be achieved by ahorn 6 as shown in FIG. 8.

FIG. 9 shows the calibration process of the sound pressure level (SPL)generated by the ultrasound transducer. In step A, when the lamp isswitched on, the value for the representative of the sound pressurelevel amplitude (SPLampI_(T)) as transmitted by the transducer is zeroand the value of the sound pressure level status (SPL OK) is zero. Saidrepresentative for SPLampI_(T) may for instance be expressed in avoltage which is put on the transducer.

In step B the first calibration cycle is started by the processingmeans, by increasing the transmitted sound pressure level amplitudevalue by incremental increase value (gain) G. In step B the transducersends an ultrasound pulse based on said SPLampI_(T) value. In steps Dand E the processor monitors during a maximum period of 20 ms if asignal is received that is greater than a predetermined threshold value.If no such signal is received after 20 ms, in step F a period of 100 msis waited, and the loop is repeated as from step B.

If in step D it is determined that a signal SPLampI_(R) is received thatis greater than a predetermined threshold value, at least two extrasmaller increases of SPLampI_(T) may be made in order to ensure that theemitted amplitude has enough margin to compensate for instance fortemperature changes. To that end, if in step G it is determined that SPLOK is not greater than 1, then in step H SPL OK is increased by 1, thevalue for the incremental increase is reduced to half the previousvalue, and after waiting 100 ms in step F the loop is repeated as fromstep B.

After these steps the final value for SPLampI_(T) is established andstored in memory in step I. This value is then used during the remainingperiod that the lamp is on, i.e. the voltage represented by said valueis put on the transducer during the light control process of the lamp asdescribed above.

The above calibration process of the SPL does not necessarily take placeon a fixed reference surface such as a table. It can also be appliedwhile the user is holding his hand in the ultrasonic beam, preferably atthe lowest point of control operation. Thereby the SPL can be set at alower level than for instance would be the case if the fixed referencesurface would be a floor. It is even possible to combine the SPLcalibration process with the control movement of the hand, anddynamically calibrate the sound pressure level while the hand is movingin the ultrasonic beam.

The process of increasing the voltage put on the transducer during thetransmission of ultrasonic pulses and measuring the voltage of thereceived reflected signals from the transducer, and increasing the SPLOK status until the threshold is exceeded is shown in FIG. 10.

There are two important issues with respect to robustness of gesturelight control based on ultrasound: acoustic issues like reflections,diffraction, fatal interference, extra noise adds to receiver, and userinterface issues like unstable objects (as shown in FIG. 11A-11C),changed (reference) objects (as shown in FIG. 12), and different objectsat the same time, etcetera.

In FIG. 11A a hand 2 is shown, which accidentally moves horizontallythrough the ultrasonic beam 4 from T1 to T3. In FIG. 11B a hand 2 isshown, which accidentally moves vertically through the ultrasonic beam 4from T1 to T3. In FIG. 11C a hand 2 is shown which moves into theultrasonic beam 4 from T1 to T2 and is held stably in said beam untilT3. It is desirable that the accidental movements as shown in FIGS. 11Aand 11B do not incur any light control actions. The action as shown inFIG. 11C however is proposed to be a user command that enables lightcontrol thereafter, as explained above with reference to FIG. 3.

In FIG. 12 a vase 7 is shown, which is put on the reference surface 3(for instance a table) between T1 and T2. Thereby the measuredtime-of-flight is shortened. On T1 lamp control is disabled (stage A),and the shortened time-of-flight will result in enablement of the lampcontrol (stage B), as explained above with reference to FIG. 3.

If however the vase 7, is in the beam 4 for more than a predeterminedperiod, for instance 1.5 seconds or longer, then it is assumed that anew reference object is placed in the beam (stage C). The measured valueis then stored as the new reference value and control is disabled (stageD).

In FIG. 13 a basic algorithm for gesture light control is shown. If wethe lamp is switched on (step A) and hardware is initialised (step B)the sound pressure level will be calibrated (step C) as described abovewith reference to FIG. 9. The ultrasonic transceiver will be sent anacoustic signal to check if a (reference) object is present and toregulate the sound pressure of the acoustic echo signal to a minimum. Ifno signal is received after a predetermined period (step D), an errorsignal is generated and presented to the user (step E).

Then a reference calibration (step F) will be performed at a fixedobstacle like a table, a floor, etcetera and is based on the firstreceived echo signal after sending a pulse to the transmitter. Otherreceived echo signals shifted in time (compared with the first receivedecho) are signals based on reflection (as shown in FIG. 1). Thesesignals are eliminated.

The reference calibration algorithm (step F) is further explained withreference to FIG. 14. A pulse is sent (step G) and the time-of-flightfrom the source to the reference surface and back to the source ismeasured (step H) and stored as TOF_(I) (step J). If no signal isreceived after a predetermined time-out period (for instance 3 seconds)(step K) after more than two attempts (step L), an error signal isgenerated and presented to the user (step M). Reproducibility of thismeasurement is checked by repeating the measurement for I=0 to I=19. Acheck is performed if the stored values for TOF_(I) (apart from the twomost extreme values) are within a predetermined threshold z (step O),otherwise the reference calibration is started again. Then the averagereference value TOF_(REF) is calculated (step P) and is stored asrepresentative of the maximum allowable distance (step Q), but only ifsaid TOF_(REF) is larger then a predetermined minimum, otherwise anerror signal is generated and presented to the user (step R). In thisexample said minimum is 32 times a predetermined minimum increment, sothat at least 32 incremental distances of a hand movement can bemeasured and translated into control instructions. During gesturecontrol no movement beyond the maximum distance represented by TOF_(REF)is expected nor tolerated. The reference distance will also determinethe control range.

After the reference calibration (step F) the system is set into a“wait-for-control-enable” state (step S), as shown in FIG. 15. Thesample frequency is reduced to 4 Hz (250 ms) (step V). The system willwait for an obstacle/object (e.g. a hand), by measuring TOF_(H) (step T,shown in more detail in FIG. 16; Time_out=100 ms) and comparing saidTOF_(H) with the reference value (step U). As long as TOF_(H) is greaterthan or equal to the reference value TOF_(REF) it is assumed that noobject is present in the beam and the system will repeat this cycle atthe sample frequency.

If TOF_(H) is smaller than the reference value TOF_(REF) twentymeasurements (for H=0 to 19) during 1 second are performed to check ifthe object is stable, by checking if the difference between TOF_(H) andthe previous measurement TOF_(H−1) is smaller than a predeterminedthreshold tx (for instance a value representing a distance of 2 cm)(step V). If this is the case the average of the measured TOF-s, TOFH(step W) is stored and the algorithm continues to the control enablestep (step X) in FIG. 13. During the control enable cycle the systemchecks if the object (hand) is still present in the beam (step X3 inFIGS. 13 and 17) and if the object is making control gestures, i.e. bymoving (step X4 in FIGS. 13 and 17), as explained in more detail withreference to FIG. 17 below. Through the above-described algorithm thesystem will not react on short (<1 second) disturbances of theultrasound beam cone during the wait-for-control-enable cycle. Acontinuous check if echo signals are received will be carried out at thereduced sample frequency.

By the proposed algorithms the control of light will be only possiblewhen the hand movement fulfils a certain profile, as exemplified abovewith reference to FIG. 3. Control is disabled when the hand is movedoutside the ultrasound beam cone (step D in FIG. 3). Control is alsodisabled when the reference object is changed, as explained above withreference to FIG. 12.

Now with reference to FIGS. 17 and 18 (wherein C and FC start with value0) the enable-control algorithm (step X) is further explained. In orderto give feedback to the user with respect to the fact that control isenabled, a visual signal is given, for example in this embodiment agreen LED (G-LED) will be switched on (step X1). The sample frequency isincreased to 40 Hz.

Based on the determined TOF the control range will be automaticallydetermined (step X2), as illustrated in FIGS. 19 and 20. Preferably thetotal number of steps Ns_(tot) is chosen such that the sensitivity ofthe system, i.e. the length of a control step, is approximately 2 cm,which corresponds to a TOF of 0.116 ms (2*0.02 m/345 m/s). A preferrednumber of control steps of 32 is proposed, so that the control range ofthe hand is 64 cm, wherein the initial position of the hand is thecentre of said range. However if the hand is closer to the source or thereference surface than 32 cm (minus a safety margin, reflected by TOFBSand TOFBR) obviously the control range cannot be 32 cm on either side ofthe hand, and the control range is shifted, for instance by locating theupper or lower limit of the control range (RangeMin or RangeMax) on therespective safety margin borders (TOFBR or TOFBS).

The time-of-flight (TOF_(C)) between the source and the hand isdetermined. Continuous checks are made to determine if the hand is stillin the beam (step X3) and if the hand is moving (step X4). If the handis not in the ultrasound beam anymore for a predetermined time, controlwill be disabled. If the hand is in the beam, but not moving for atleast one second, it is checked if prior thereto light properties havebeen controlled (FC>0). If this is the case, the FC is reset to 0 andcontrol is disabled. If this is not the case, the control mode isswitched to controlling a different light property, indicated by FCbeing raised by 1, and the algorithm returns to TOF_(C) determinationloop.

If it is determined that the hand is moving (step X4), and then it ischecked if the TOF_(C) is within the calculated range (step X5). IfTOF_(C) is outside said range clipping takes place (step X6), forinstance by replacing TOF_(C) with the nearest maximum value, asillustrated in FIG. 21. The direction (step X7) and the number of stepsNs_(act) (step X8) is calculated, which is used to translate thephysical hand position into a digital position value for controlpurposes.

Ns_(act) is calculated by dividing the difference in the measured TOF(TOF_(C)−TOF_(C−1)) by TOF. These values are translated to a drivesignal sent to the LED drivers to control the light properties. Thecurrent value of FC determines which one of the light properties iscontrolled (step X9). In this example there are only two properties tobe controlled: “basic control” and “fine control”, but this can beeasily extended. This control loop for controlling a light property isrepeated until control is switched off, or until FC is raised so that adifferent light property is controlled.

Three different methods are proposed as examples for selecting the lightproperties to be controlled, based on a menu structure. In the firstmethod the selection of the basic light controls will be based on thefreezing of the object (i.e. hand 2) during for instance 1 second. Thesecond method of selection of the basic controls is based on rotation ofthe hand. The third method of selection in menu control for basic lightcontrols is based on the hand crossing the ultrasound beam in horizontaldirection (assuming that the ultrasound beam extends in verticaldirection).

With these methods the basic light controls can be selected in asequential manner, as illustrated in FIG. 22. This means that if a userfirst selects a light colour (from 1 s to 1.8 s), the control selectionis moved on towards control of the colour temperature of the chosencolour 1 second later (at 2.8 s). Control of colour temperature is thenalso achieved by hand movement (from 2.8 s). The control range is chosenthe same as used for the previous basic control.

FIGS. 23-28 shows as an example the different steps in a menu for threebasic LED light controls. In FIG. 23 the colour is controlled byup-and-down movement of hand 2. In FIG. 24 the hand 2 is frozen atspecific desired colour for 1 second, so that said specific colour ischosen, and control selection is switched to colour temperature controlin FIG. 25. In FIG. 26 the hand 2 is frozen at a specific desired colourtemperature again for 1 second, so that said specific colour temperatureis chosen, and control selection is switched to intensity in FIG. 27. InFIG. 28 hand 2 is frozen at a specific desired light intensity, so thatsaid specific light intensity is chosen, and control is switched off.

Switching from one basic control to another one can also be achieved bymaking a hand rotation. Therefore a certain angle between hand andultrasonic beam has to be made (see FIG. 29). If the angle between handand ultrasound bean cone is 90 degrees the maximum echo signal will bereceived by the ultrasound transceiver. If the hand makes an angle of 45degrees with the ultrasound beam cone (almost) no echo signal will bereceived by the transceiver, because the echo signal will be reflectedby the hand to another position. A certain unique profile can be chosenfor selecting one of the basic controls in a menu, for example as shownin FIG. 29.

With this method the user can switch from one basic control to anotherone without the need to control each basic control. Stepping through themenu is done by another type of

Selection of a basic light control can also be achieved by (horizontal)hand movements crossing the ultrasound beam cone, as illustrated in FIG.30. The time-of-flight is measured with a high sample rate, and analternating TOF signal (low-high-low, etcetera) is recognized as aunique profile, which can be chosen for selecting the basic controls ina menu.

In a light remote control system, before, during or after the userinputs light control instructions feedback or messages will be given tosaid user, comparable to TV applications where feedback is given via thedisplay to the user during control of the basic functions like contrast,brightness, saturation, etcetera. For example if the light system doesnot receive the control signal, or the signal is too weak, a certainerror messages to the user is desirable.

Depending of the used light control application like remote control,ultrasound or video based gesture light control, different feedbackmechanisms are proposed.

In a menu controlled system changes have to be made visible for theuser. Also when control is enabled feedback has to be given. If an erroroccurs also feedback has to be given to the user. Also different kindsof error messages can be given to the user or to a service environmentfor fast analyses and repair of the error.

The first proposed method for feedback to the user is messaging by lightpulses, or flickering of light.

Eyes are very sensitive for light flicker until frequencies around 60Hz. Flicker can be made by switching the light off and on again veryfast. A alternative method to create light flicker is reducing lightintensity for a very short moment in time and change it back to theoriginal light intensity.

The second proposed method for feedback to the user is messaging bylight colour changes or colour temperature changes. Different colours orcolour temperature could give different messages to end-user. Also acombination of the first two methods can communicate extra informationto the user.

The third proposed method is to make text feedback using a LED arraylamp. By placing the LEDs in an array as shown in FIG. 31, array textmessages can be formed. Also icons can be formed. FIG. 31 shows anexample of a message text “E2”, which could be a certain error message.In this manner the LED lamp is used as a display to send different textmessages to the user or service department during an error situation.

As shown in FIG. 32, the text of the LED array can also be projected bya lens 8 on an object surface (reference 3) like a table, a wall orfloor. In an ultrasound based gesture light control system as describedabove the distance between the lens 8 and the object (the focal lengthf) by the TOF measurement of the ultrasound sensor 5 (here shown builtin the lens 8) can be used. With this information the focal length canbe adjusted as function of the distance with the object (automaticfocus). For example a stepper motor can perform the adjustment of thefocal length. The text of the lamp array has to be mirrored if a lens isused.

In order to reduce the costs of the lamp to a minimum and to have thepossibility to control all possible lighting parameters like colour,intensity, etcetera, the electronic circuit needed for carrying out thecontrol functions is integrated in the lamp. The microprocessor used forgesture control is also integrated in the LED control microprocessor toreduce the cost even more. The integration of the ultrasound sensor inthe lamp makes low cost, high volume production possible.

With reference to FIG. 33, as explained above the micro-controller sendsa pulse to the ultrasound transmitter of the ultrasound transceiver 5. Adigital pulse signal is generated by the control part 13A of amicro-controller 13, and converted by DA-converter 17 in saidmicro-controller 13 into an electric pulse. This pulse will be amplifiedby the amplifier 18 in the pre-processor 10 (shown in more detail inFIG. 34) to a value that can be used by the ultrasound transmitter partof the ultrasound transceiver 5. Then the piezo-electric ultrasoundtransceiver 5 sends an acoustic signal (for instance at a frequency of40 kHz). An object will reflect this acoustic signal. The pre-processor10 will receive the reflected signal via the ultrasound transducer 5. Inorder to reduce the influence of outside disturbances the signal isfiltered by a 2nd order High-Pass filter 11 of for instance 20 kHz(=fc). After filtering the signal is amplified by amplifier 12 in thepre-processor 10.

Microcontroller 13 comprises a comparator 14, which creates a digitalpulse signal from the electric signal received from the pre-processor10, which can be processed by the micro-controller 13.

The micro-controller 13 further comprises a LED driver part 13B, with amodulator 20, which is connected to the LED driver 19, and part of theROM 15 and the RAM 16, which is shared, with the control part 13A of themicro-controller.

Such a micro-controller 13, arranged to drive a LED, is well known inthe art, but is further programmed to perform the control functions asdescribed above. The micro-controller can be a simple processor, forinstance of the 8051-family. The size of the ROM 15 can be as low as 2kB and the size of the RAM 16 can be as low as 256 bytes.

FIG. 35 shows a lamp according to the invention comprising a housingwith a standard incandescent lamp type fitting, ten LEDs 21 arranged ina circle, a transducer 5 in a horn 6. All the electronic components likethe micro-controller 13, pre-processor 10 and LED driver 19 are built-inin the housing 23. Thereby a very compact lighting system is obtained,which requires no further external accessories to be operated andcontrolled.

Although the invention is described herein by way of preferredembodiments as example, the man skilled in the art will appreciate thatmany modifications and variations are possible within the scope of theinvention.

1. A lighting system comprising: a lamp arranged to transformelectricity into a light beam having properties including intensity,colour, colour temperature, direction and beam cone angle; a lightcontrol system arranged to adjust said light beam properties; anultrasonic transmitter arranged to transmit ultrasonic signals; anultrasonic receiver arranged to receive reflected ultrasonic signals;and a processing system arranged to derive a time-of-flight signalrepresenting the time differences between said transmitted and receivedultrasonic signals and to send control signals to said light controlsystem in dependence of said time-of-flight signal, wherein saidprocessing system is further arranged to perform a reference calibrationstep, wherein the time-of-flight (TOF) signal is repeatedly measured fora multitude of times, and wherein the processing system determines if adeviation of the majority of the measured time-of-flight values (TOFI)of said multitude of measurements is lower than a predeterminedthreshold (z), and wherein said processing system is arranged tocalculate the average (TOFREF) of said measured time-of-flight values(TOFI) and store said average (TOFREF) in a memory device as a referencetime-of-flight value if said deviation is lower than said threshold (z).2. The lighting system of claim 1, wherein said processing system isarranged to generate an error signal if said deviation is not lower thansaid threshold (z).
 3. The lighting system of claim 1, wherein saidprocessing system is arranged to store said reference time-of-flightvalue (TOFREF) in said memory device only if said referencetime-of-flight value (TOFREF) is greater than a predetermined minimumvalue.
 4. The lighting system of claim 1, wherein said processing systemis arranged to generate an error signal if said reference time-of-flightvalue (TOFREF) is not greater than a predetermined minimum value.
 5. Thelighting system of claim 1, wherein said processing system is arrangednot to store a reference time-of-flight value (TOFREF) in said memorydevice if during said reference calibration step no signal is receivedby said ultrasonic receiver during at least a predetermined number oftime-of-flight measurements.
 6. The lighting system of claim 1, whereinsaid processing system is arranged to generate an error signal if duringsaid reference calibration step no signal is received by said ultrasonicreceiver during at least said predetermined number of time-of-flightmeasurements.
 7. A lighting system comprising: a lamp arranged totransform electricity into a light beam having properties includingintensity, colour, colour temperature, direction and beam cone angle; alight control system arranged to adjust said light beam properties; anultrasonic transmitter arranged to transmit ultrasonic signals; anultrasonic receiver arranged to receive reflected ultrasonic signals;and a processing system arranged to derive a time-of-flight signalrepresenting the time differences between said transmitted and receivedultrasonic signals and to send control signals to said light controlsystem in dependence of said time-of-flight signal, wherein saidprocessing system is arranged to perform a wait-for-control-enablementcycle wherein said time-of-flight (TOF) is repeatedly measured atpredetermined intervals and to compare said measured time-of-flightvalue (TOF) with a reference time-of-flight value (TOFREF) which isstored in memory during said wait-for-control cycle, and to repeat saidmeasurement if said measured time-of-flight value (TOF) is equal to orlarger than said reference time-of-flight value (TOFREF), and whereinsaid processing system is further arranged to determine if the measuredtime-of-flight value (TOF) is smaller than said reference time-of-flightvalue (TOFREF) and if the deviation between the measured time-of-flightvalue (TOFH) and the previous measured time-of-flight value (TOFH−1) islower than a predetermined threshold (tx), and said processing system isarranged to send control signals to said light control means independence of time-of-flight signals derived after it is determined thatthe measured time-of-flight value (TOF) is smaller than said referencetime-of-flight value (TOFREF) and that said deviation is lower than saidthreshold (tx) for a predetermined number of repeated measurements. 8.The lighting system of claim 7, wherein said predetermined interval issubstantially larger if it is determined that said measuredtime-of-flight value (TOF) is equal to or larger than said referencetime-of-flight value (TOFREF), than if it is determined that saidmeasured time-of-flight value (TOF) is smaller than said referencetime-of-flight value (TOFREF).
 9. The lighting system of claim 7,wherein said processing system is arranged to calculate the average ofsaid measured time-of-flight values (TOF) and to store said average(TOFH) in a memory device, and the processing system is arranged to sendcontrol signals to said light control system in dependence on a positiveor negative difference between the measured time-of-flight (TOF) andsaid average time-of-flight (TOFH) after it is determined that saiddeviation is lower than said threshold (tx) for a predetermined numberof repeated measurements.
 10. The lighting system of claim 9, whereinsaid processing system is further arranged to clip the difference of themeasured time-of-flight value (TOF) to a maximum allowed positive ornegative difference between the measured time-of-flight (TOF) and saidaverage time-of-flight (TOFH) for the purpose of determining the controlsignals to be sent to the light control system.
 11. The lighting systemof claim 9, wherein said processing system is further arranged tocalculate said maximum allowed positive and negative difference suchthat the negative difference is smaller than said average time-of-flight(TOFH), and that the positive difference is smaller than the differencebetween said reference time-of-flight (TOFREF) and said averagetime-of-flight (TOFH).
 12. The lighting system of claim 11, wherein saidprocessing system is further arranged to adapt the determination of thecontrol signals to be sent to the light control system such that a fullrange of control signal is achieved within a calculated range of themaximum allowed positive and negative difference.